1. Field of the Invention
This invention relates to single lens reflex camera bodies, and more particularly to the use of plastic in such a body.
2. Description of the Prior Art
In general, camera bodies which are formed from the viewpoint of providing high precision accuracy and rigidity will make use of light alloy castings such as those made with aluminum. The manufacturing of such die-cast camera bodies usually involves a great number of machining steps, and is therefore very time-consuming and laborious, causing such items to be necessarily expensive.
Therefore, in the art of moderately priced cameras (generally of the lens shutter type) which do not demand such high precision accuracy, the use of plastics in the bodies has been given consideration. At the present time, due to the great advance in plastic technology, as far as moderately priced camera bodies are concerned, sufficient precision accuracy and rigidity is achieved only by the use of plastics.
On the other hand, even in the art of single lens reflex cameras, since reduction of the weight and lowering of the production cost are desired objectives, the use of plastics in the camera body has also been given consideration. However, in single lens reflex cameras which require high precision accuracy, the presently developed state of plastic techniques has not yet reached a level which will assure sufficient precision accuracy when used in the body of the single lens reflex camera. If the camera body were made of plastics, problems would arise in that there would be a high possibility of occurrence of accidents due to the insufficient strength of the body and due to deformation thereof with variation of the ambient temperature.
For this reason, recent use of plastics in the single lens reflex camera has involved provision of means for assuring at least the precision accuracy of the so-called flange back, or distance from the mount surface of the attachment base for the photographic objective lens to the film guide rail. Such means have involved use of a metal block having a portion in which are formed an aperture for defining the film frame size and film guide rails and a bottom wall portion having tripod screw-threads which is inserted into and seated in between the plastic-molded takeup spool and cartridge chambers of the camera body. The device is then assembled with a front panel of metal having a lens mount to complete the body of the single lens reflex camera.
Since the front panel of the single lens reflex camera is usually provided with the mirror box, according to the prior art, the lens mount attachment base and the wings are formed as an aluminum die-cast member, while the mirror box is also formed separately as an aluminum die-cast member, and then both the castings are assembled to form the front panel. This two-casting form of front panel, however, necessitates not only assembly line operators, but also a secondary machining step during assembly, and an additional finishing step for assurance of the required precision accuracy.
On this account, attempts have been made to form the lens mount attachment base, the wings and mirror box as a single aluminum die-casting. But this single-casting form of front panel also necessitates the additional finishing step for assurance of the required precision accuracy.
Therefore, recently, the mirror box has been made up of metal by pressing means, while the lens mount attachment base and the wings are formed as a zinc die-casting, and then both the units are assembled with each other to form a front panel. This new two-unit form of front panel, because it uses a mirror box of pressed metal enables the size and position of each hole on the mirror box in itself to be determined with high accuracy in machining, and because the lens mount attachment base and wings are made as a zinc die-casting, it enables reduction of the number of additional machining operations.
Although this new front panel having a two-component structure provides advantages, it nevertheless necessitates an assembly operation for formation of the two-component unit. Another disadvantage arising from the use of zinc die-casting is that weight is significantly increased as compared with aluminum die-casting.
It is, therefore, a first object of the present invention to eliminate the above-described drawbacks and to form a lens mount attachment base and wing portions of plastic, while the mirror box is formed of metal, wherein the metal portion and plastic portion constitute a front panel, and wherein said front panel is assembled in a camera body.
A second object of the present invention is to provide a front panel as a portion of the camera body in a plastic-molded unit form.